Torque balancing motor control



March 30, 1965 P, s, LUND 3,176,206

TORQUE BALANCING MOTOR CONTROL INVENTOR.

PHILIP S. LUND FIG. I

ATTORNEY March 30, 1965 P. s. LUND TORQUE BALANCING MOTOR CONTROL 2 Sheets-Sheet 2 Filed June l2, 1961 FIG. 2

ATTORNEY United States Patent O 3,17o,26 TURQUIE EALANCENG MO'R QGNTRL Philip S. Lund, Grand Rapids, Mieli., assignor to Honeywell Inc., a corporation oi Delaware Filed lune 12, 196i, Ser. No. 116,534 Claims. (Cl. S18-32) This invention relates to improvements in signal generators and torque generators integrated on the same Core and more particularly to means for reducing the magnetic interaction between signal Generators and torque generators integrated on the same core.

Devices such as gyroscopes, accelerometers, or similar devices which have a member that rotates or moves in relation to a reference due to some force which is to be measured or which is otherwise applied generally utilize some device such as a signal generator to detect or measure this rotation or movement and produce a voltage representative of it. Generally, the signal generator consists of a stationary member' with a primary and secondary winding on it and a rotor or armature connected to the rotatable or movable member of the gyroscope or other device. A movement of the rotor then changes the llux linkage between the primary winding and the secondary winding on the stator of the signal generator. A device known as a torque or torce generator is generally utilized in devices such as gyroscopes and accelerometers to maintain the movable member near its null position. In many cases the torque generator is a device similar to the signal generator except that an alternating voltage is applied to both the primary winding and the secondary winding on the stator to produce a torque on the rotor which is connected to the movable member of the gyroscope or other device.

It can be seen that much space and manufacturing costs would be saved if a single stator and rotor were used for both the signal generator and the torque generator. However, in prior art devices which attempted to integrate the signal generator and the torque generator on the same stator much trouble arose because of interaction between the flux produced by the torque generator that produced by the signal generator. Also, it was very difficult to manufacture the device so that the signal generator was at a null at the same mechanical position that the torque generator was at a nul In most cases the output of the signal generator is fed to an amplifier and the amplified signal is then fed to the control winding or input of the torque generator. in this manner when the signal generator is oli null, or the rotor has rotated some degree, the signal generator generates a signal which is amplified and sent to the torquer. The torquer then produces a torque on the rotor which tends to turn it back to the null position. In this manner the device which the rotor is connected to is kept near its null position. However, due to the interaction between the signal generator tlux and the torque generator ilux if the gain of the ampliiier, amplifying the signal of the signal generator, is too high the entire device will tend to oscillate. Because of the improvements incorporated in the present device the gain of this amplifier may be increased by at least a factor of twenty without adverse oscillation.

In the present invention the stator is a cylindrical device having a plurality of poles radiating inward toward a central axis, and forming a central aperture there- 3,l7,2@h Patented Mar. 3), 1965 between. The rotor is a cylindrical device having half the number of poles that the stator has, radiating outward from a central axis, and rotatably mounted within the central aperture formed by the stator. The poles of the stator are divided into four equal quadrants. The primary and secondary windings of the signal generator are wound around the poles of two diametrically opposite quadrants. The primary and secondary of the torque generator are wound around the poles in the other two quadrants. ln addition to these four windings there is a balance winding and a compensation winding both of which are wound around the same poles as the torque generator windings. The purpose ofthe compensation winding is to provide a means for compensating for unwanted torques on the rotor, or in other words, torques which are not produced by the torque generator. The purpose of the balance winding is to compensate for magnetic interactions between the signal generator and the torque generator. By adding a variable transformer to the circuitry to compensate for the physical difference between the signal generator nulls and the torque generator nulls a highly accurate and extremely sensitive device has been provided.

Accordingly, it is an object of this invention to provide an improved control apparatus.

Another object of this invention is to provide a control apparatus with an increased sensitivity and gain.

Another object of this invention is to provide a means of electrically and magnetically separating the signal generator and the torque generator of this control apparatus, while maintaining them on the same stator.

Another object of this invention is to provide a means for adjusting the null or the signal generator to coincide with the null of the torque generator.

rl`hese and other objects of the present invention will be understood upon consideration of the accompanying specication, claims, and drawings of which:

FIGURE l is a somewhat schematic diagram of a gyroscope showing the position of the torque generator and signal generator;

FIGURE 2 is a winding diagram of the stator or" the torque generatorsignal generator; and

FIGURE 3 is a schematic diagram of the signal generator-torque generator.

Referring to FIGURE 1 a gyroscope is shown in a somewhat schematic representation and a typical use of the present control apparatus is shown. The gyro has a spin motor designated M which spins within a gimbal about the spin reference axis designated SRA. The gyroscope also has an input axis designated 1A perpendicular to the spin reference axis SRA and an output axis designated OA mutually perpendicular to the spin reference axis SRA and the input axis IA. A schematic means for mounting the gimbal on the gyro case is shown and the present control apparatus is shown schematically mounted on the output axis. The rotor of the control apparatus is mounted on the output axis so that any movement of the gimbal about the output axis causes the rotor to move Within the winding of the control apparatus. A signal generator is shown schematically as one winding designated SG. A torque generator is shown schematically as a single winding utilizing the same rotor as the SG, this winding being designated TG. In FIG- URE l, the output of the signal generator SG is fed through an ampliier A to the input of the torque generatorque.

increased.

arranco tor TG. yThis is the normal manner of connecting a in amplifier A and fed to the torque generator TG. The

torque generator then produces a torque on the rotor of 'the opposite sense from the precessional torque. A state of equilibrium is reached where the torque from the TG is equal and opposite to the gyroscopic precessional As is well known, the current applied to the TG may be used as a measure of the rate of movement of the gyro about the IA.

If it is desired to maintain the spin motor of the gyroscope in a closer proximity to its original position about the output axis, the gain of the feedback loop must be That is, the gain of the amplifier must be increased so .that smaller signals from the signal generator SG will have more effect on the ltorque generator TG.

However, as the gain of the amplifier is increased small undesirable signals such Ias magnetic coupling between the torque generator TG and the signal generator SG are 'ampliiied more and the entire feedback loop (as well as the control system controlled by the gyroscope) has a tendency to oscillate.

Referring to FIGURE 2, an end view of the signal generator-torque generator has been shown in which one turn of each winding is shown for simplicity. It should be remembered that this single turn for each winding simply 'shows the manner in which the winding will be wound and in actuality each winding has many turns. The stator designated is comprised of an outer cylindrical member 10 having sixteen uniformly spaced salient poles numbered consecutively 11 through 26. The sixteen Y poles 1.1 through 26 are connected to or are an integral part of the inner surface of cylindrical member 10 and radiate inwards toward a central axis. The ends of the uniformly spaced salient poles 11 through 26 form a central aperture in which is mounted rotor 30.

Rotor 30 is concentrically mounted within the aperture formed by poles llthrough 26 by means of a centrally located hole 29. The central hole 29 in rotor 30 is simply for mounting rotor 30 to some device such as the gyroscope as shown in FIGURE l. It should be understood that any convenient means for mounting rotor 30 for rotation can be used and that central hole 29 is simply one convenient method. Rotor 30 has eight poles numbered consecutively 31 through 38 and uniformly radiating outwardly from the central axis. Poles 31 through 38 of rotor 30 radiate outwards towards poles 11 through 26 of stator 10 and are of such a length as to form a'uniform air gap therebetween. In this preferred embodiment, each of the poles 31 through 38 on rotor 30 are approximately as Wide as each of the poles 11 through 26 on stator 1li. v

The signal generator consists of two windings namely a primary winding and a secondary winding. The priu maryrwinding is comprised of two coils 40 and '41 and the secondary winding is comprised of two coils 42 and 43. ln FIGURE V2 one turn of each coil will be discussed and one turn of eachcoil-is shown. However, it should be remembered that each coil has many turns and one turn is used simply for convenience. Also, al1 of the f rest of the turns of each winding will be wound exactly as the one turn shown is wound. In fact, each'of the turns shown can be thought of as a complete winding made up of a number of turns of wire approximately the size of the lead wires shown in FIGURE 2. If the stator is divided into imaginary quadrants so that poles 13 through 16 are contained within a iirst quadrant, poles '17through 29 are contained within a second quadrant,

poles 21 through 24 are contained within a third quadrant and poles 25 through 12 are contained within r1 fQurth quadrant, then the signal generator windings will be wound on poles within the irst and third quadrants. It should be noted that the signal generator could be wound on any diametrically opposite set of poles equally well. Each winding, as shown in FIGURE 2, consists of two small wires attached to the larger winding. The larger winding can be thought of as containing a number of turns of the smaller wires. The windings are actually wound inthe direction in which the small wire approaches the larger winding.

Coil 46 of the primary winding of the signal generator is wound in a manner such that it forms three loops. The first loop encompasses pole 13 of stator 10, the second loop encompasses poles 14 and 15 of stator 10, and is wound in the opposite direction of the rst doop, and -the third loop encompasses pole 16 of stator 1t) and :is wound in the same direction :as the irst loop. Coil 41 is Wound in a manner similar to coil 4t). The `first loop of coil 41 encompasses pole 21 of stator iltl, the second loop encompasses poles 22 and 23 of stator 10 and is wound in a direction opposite to the direction of the first loop, and thev third -loop encompasses pole 24 `of stator 10 and is wound in the same direction as the rst loop. One side of coil 40 is connected -to a terminal 46 by means of a lead 50 and terminals 46 and 45 are connected together by some convenient means such as a solder lug. The other side of coil 40 is connected to a terminal designated number 47 by a lead 49. One side of coil 41 is connected to a terminal 44 by means of a lead 4S and the other side of coil 41is connected to terminal 45 by means of a lead 51.

In all of these windings it should be remembered that the coils are actually comprised of a number of turns ot wire, which the connecting leads are actually a continuation of, and the coils are wound in the direction in which the lead wire enters the coil. For example, lead 49 enters coil 4t) in a clockwise direction and coil 4t? would be wound in that manner, starting where llead 49 enters coil 40 proceed under poles 15 and 14, over pole 13 and around it, under pole 13, over pole 14 and pole 15, under pole 16 and around it. Arter a plurali-ty of turns in this manner the wire leaves coil 40 in a direction designated by lead 50.

The secondary winding of the signal generator consists of coils 42 and 43. Coil 42 is connected toa terminal 55 by means of a lead 56. Coil 42 forms a tirst loop about poles 13 and 14 and .a second loop about poles l5 and 16. rPhe -second Iloop of coil 42 is wound in the opposite direction of the lirst loop of coil 42. A lead 57 connects the other side of coil 42 to la terminal 58. Terminal 58 is connected to another .terminal 59 by some convenient means such 4as a lug or a small portion of wire. Terminal 59 connects to one side of coil 43 by means of a lead designated 60. Coil 43 is similar to coil 42 in that it forms a rst and second loop. The rst loop is about poles 21 and 22 and the second loop is wound in the opposite direction about poles 23 and 24. 'Iihe other side of coil 43 connects by means ofra lead 61 to the terminal 62.

The torque generator lhas va pattern winding consisting of coil 67 'and coil 71 and a cont-rol wind-ing consisting of coil 77 and coil 8.2. Coil 67 of the pattern winding of the torque generator connects to a terminal designated 65 by means of a lead 66. Coil 67 forms two loops one of which encompasses poles y17 and 18, and the other of which encompasses poles 19 and 20 `and is wound in the opposite direction of the rst loop. The other side of coil 67 connects to a terminal designated 69 by means of a lead 68. Terminal 69 is also connected to coil 71 by means of a lead 70. Coil 71 is similiar to coil 67 in that it forms two loops, one tof which encompasses poles 25 and 26 and the other of which encompasses poles 11 and 12 and is wound in the opposite manner of the iirst loop. The other sideA of coil 71 connects to aY termina-l Ydesignated 73 by means of .a ylead '72. Coil 77 of the control winding of the torque generator is connected to atermin-al designated as 75 Vby means of a lead 76. Coil 77 adsense forms three loops namely a rst loop encompassing pole 17, a second loop encompassing poles i3 and l@ and Wound in the opposite direction as the first loop, and a third loop encompassing pole Zt? and Wound in the same direction as the tirst loop. The other side ot coil 77 is connected to la terminal designated 79 by means of la lead 73. Terminal 79 connects to a terminal titl' by some convenient means such as a lug. Terminal dit is connected to coil 32 by means of a ilead Sl. Coil 82 is similar to coil '77 in'that it forms three loops, a first loop encompassing pole 25, a second loop encompassing poles 2o and lll and wound in the opposite direction from the lirst loop, and a third loop encompassing pole 12 wound in the same direction as the first loop. The other side of coil 82 is connected to ya terminal designated 84 by means of a lead d3. These windings are also schematically shown in FlGURE 3.

Also encompassing the poles contained witlnn the i second and `fourth quadrants of the stator l@ are a `compensation winding `consisting of coils 9d and 9% and a balance winding consisting of coils S7 yand S?. Coil S7 of the balance winding forms three loops the iirst of which encompasses pole 17, the second of which encompasses poles ld and i9 .and is wound in an opposite direction from the irst loop, and the third loop which encompasses pole Ztl and is Wound in the same direction as the first loop. One side of coil 87 is connected to a terminal designated d by a lead do and the other side of coil S7 is connected to terminal d2 by a lead titl. The other coil Si? of the balance winding is wound similar to coil 37 in that it forms three loops. The ret loop encompasses pole l2, the second loop encompasses poles lill and 26 and is wound in the opposite direction from the first loop, and the third loop encompasses pole Z5 and is wound in the same direction as the first loop. One side of coil 89 connects to terminal 62 by means of lead S8 [and the other side `of coil 89 connects to a terminal designated @l by means of a lead gli.

Coil gli of the compensation winding is wound in a manner to form three loops. The first loop encompasses pole i7, the second loop encompasses poles 18 and l@ and is wound in the opposite direction of the rst loop, and the third loop encompasses pole 2@ and is wound in the same direction as the irst loop. One side of coil 9d connects to a terminal desigated 92 by means of a lead 93. The other side of coil 94 is connected by means of a lead 95 to a terminal 9d. Terminal 96 is also connected by means of a lead 97 to the 'other coil 98 of the compensation winding. Coil 9S is wound similar to coil gli in that it forms three loops. rThe iirst loop encompasses pole l2, the second loop encompasses poles lill and 2o and is Wound in the opposite direction of the tirst loop and the third loop encompasses pole 2S and is Wound in the same direction as the irst loop. The other side of coil 9% connects to a terminal ltill by means of a lead 99. All of the windings shown in FIGURE 2 can be seen schematically v Vin FlGURE 3 and are numbered correspondingly.

'ln FIGURE 3 all of the windings previously described are shown schematically as comprising a single transformer. lt should be understood that the core of this schematic transformer would be comprised of stator lll and rotor 3i). A terminal board designated as lllll shown schematically in FIGURE 3 as a separate terminal board would actually be the outer case or stator of the control apparatus as shown in FIGURE 2.

A Variable transformer designated as lll in FGURE 3 consists of a primary winding llZ and a secondary Winding 122. One side of primary winding i12 connects to a resistor ildby means of a lead M3. The other side of resistor llt connects to a terminal 116, on a terminal board designated 12d, by means of a lead its?.

The other side of primary winding il?, of Variable transformer lll connects to a terminal 47 on terminal board 114i through a lead M3. The signal generator primary winding circuit is then completed by connecting terminal dft on terminal board il@ to a terminal l2?. on terminal board l2@ by means 'of a lead 119. Terminals llo and lil are adapted to have an alternating voltage applied thereto. The secondary winding 122 of variable transformer lll connects to a terminal M3 on terminal board 126 by means of a lead 124. The other side of the secondary winding 122 of Variable transformer lill connects to the center tap of a variable resistor 126 by means ot a lead i125. One side of the resistive element of Variable resistor lie connects to one side of a resistor 12S through a lead The other side of resistor 12S connects to terminal 9i on terminal board lltl through a lead 129. The other side of the resistive element of variable resistor 1265 connects to a resistor ll through a lead 136. The other side of resistor 131 connects to terminal 85 on terminal board liti through a lead L32. Terminal 133 on terminal board l2@ connects to terminal 55 on terminal board il@ by means of a lead 13d. One side of a capacitor 13S is connected to lead 124 and the other side of capacitor i353 is connected to lead 13d- The secondary circuit oi the signal generator is completed by attaching a load, not shown, across terminals 133 and lZZ` on terminal board 126. ln normal usage this load would consist of an amplifier, because on the average the signal from the signal generator is too small tor normal usage without amplification.

Terminal e5 of terminal board lli? connects to a terminal 137 on a terminal board l35 by means of a lead 1136. Terminal 73 on terminal board il@ connects to one side of a capacitor i139 by means of a lead 138. Capacitor i3@ is in series with a resistor lll@ the other side of which connects to another resistor 142 by means or a lead ldl. The other side of resistor M2 connects to a terminal on terminal board l35 by means'of a lead 3.4.3. Terminals 137 and .ld-4 on terminal board M5 are adapted to have an alternating voltage applied thereto. in this manner, by means of the aforementioned circuitry, the torque generator pattern iield winding may be energized.

The compensation winding, coils 98 and 95.-, is connected in series with the torque generator pattern eld winding by connecting it in parallel with resistor M2. This is accomplished by connecting terminal lill) of terminal board .lid to one side of resistor 3.42 by means 'of a lead i145, and by connecting terminal 12 ot terminal board il@ to the other side of resistor M2 by means of a lead Sido.

Terminal 75 on terminal board lid is connected to a terminal ll on terminal board M5 by means of a lead ll. Terminal on terminal board ll@ is connected to a terminal lSS on terminal board i355 by means of a lead i593. Terminals f5?. and T153 are adapted to have an alternating voltage applied thereto. The alternating voltage to be applied to terminals lh and 153 normally comes from an amplifier, not shown, connected across terminals 123 and i3?, on terminal board liti. The amplier feedback circuit just described is shown somewhat schematically in FlGURE 1.

Operazion The rotor Se as shown in FIGURE 2 is in the null position for both the signal generator and the torque generator. Assume that an alternating voltage is applied to terminals llo and 123 on terminal board I Ztl. Also,

assume for the moment that terminal llZl is positive and, neglecting the eiects of resistor lill and variable transformer lll for the moment, terminal d on terminal board llo will be positive while terminal 47 on terminal board lli) will be negative. rl`hus, current will dow from terminal ill through lead dit, through coil 41, lead 5l, to terminal 45, from terminal 4S through the lug to terminal d6, through lead Si) to winding 40, from the other side of winding through lead 49 to terminal 47. This lwill, momentraliy, canse pole 2l to look like a south pole, pole 22 to look like a north pole, pole 23 to thereto.

look like a north pole, and pole 24 to look like a south pole. Since pole 36 of rotor 31B is exactly between pole 21 and pole 22 of stator 10 the tlux which llows out of pole 22 will ow into 36 of rotor 30 and back into pole 21 of stator 1G. Thus, it can be seen that the net voltage induced in the portion of coil 43 which is wound around poles 21 and 22 will be zero. The flux ilowing out of pole 23, which is momentarily a north pole, will ow into pole 37 of rotor 30 and back into pole 24, which is momentarily a south pole. Thus, the eirect on this loop of coil 43 is also zero. It can be seen that the net etect ofthe flux flowing out of pole 13 of the stator into pole 32 of the rotor 3o and back into pole 14 of the statort10 will be zero, and the tlux owing out of pole 16 of stator 16 into pole 33 of rotor 311 and back into pole 15 of stator 1t) will Yalso be zero. Thus, the net voltage induced into the coils 42 and 43 of the secondary winding Y of the signal generator is zero and the signal generator is at a null. When the alternating voltage on terminals 116 and 121 of terminal board 12@ changes so that terminal 121 is negative all of the poles of the signal generator will be exactly opposite magnetically to the foregoing explanation so that the signal generator will still be at a null when the rotor is at the position in which it is shown in FIGURE 2.

However, if the device to which the rotor 3o is attached should turn and thereby cause the rotor to turn so that pole 32 of rotor 30 is aligned radially with pole 14 of stator 10, pole 33 of rotor 3@ is aligned with pole 16 of stator 1&1, pole 36 is aligned with pole 22 of stator 10', and pole 37 of rotor 31) is aligned with pole 24 of stator 10, the signal generator would no longer be at a null position. Assuming terminal 121 of terminal board 1211, and hence terminal 410i of terminal board 111i, is still positive, but becoming less positive, the current will ow through the signal generator primary winding as already described. That is, from terminal 44 through coil li1 and through coil 40 to terminal 47 on terminal board 110. This will cause pole 16 of stator 1@ to act as a north pole while pole 14 of stator 11B acts as a south pole. Thus, flux will tlow from .pole 16 of stator 10 to pole 33 of rotor 30, through rotor 3G to pole 32, and into pole 14 of stator 1@ to complete the flux path. Since poles 13 and 15 are not radially aligned with a pole of the rotor, no flux will flow from these poles. lt can be seen that a net voltage will be induced in coil 42 which will tend to make current ilow in the circuit from terminal 58 to terminal 55. Simultaneously the current in the primary winding makes pole 22 of stator 10 a north pole and pole 24 of stator 111 a south pole. Thus, ux will flow from pole 22 of stator 10' into pole 36 of rotor 30, through rotor 311 to pole 37, and back into the stator by way of pole 24 to complete the flux path. Thus a net voltage will be induced into coil 413 which will tend to make current in the circuit flow from terminal 62 to terminal 59. Therefore a net output voltage will be produced. A net output voltage would also be produced if terminal 47 on terminal board 110 is positive but becoming less positive. This is true because all the poles of the signal generator would be reversed magnetically to the explanation above. That is, the north poles would then be south poles and the south poles would then be north poles.

As has already been explained, terminals 137 and 144 on terminal board 135 are adapted to have an alternating voltage applied at all times that the control apparatus is energized. Neglecting for the moment the effects of the compensation winding which is in series with the torque generator pattern field winding and wound on the same poles, terminals 65 and 73 on terminal board 110 can be assumed to have an alternating voltage applied directly thereto. Also, assume that terminals 153 and 151 on terminal board 135 do not have a control voltage applied That is, the torque generator control eld windings 77 and 82 are not energized. When terminal 73 on @a terminal board 111B` becomes positive the current will tiow through coil 71 and coil 67 in such a manner as to make poles 17, 13, 25 and 26 south poles and poles 19,

20, 11 and 12 north poles. Thus, it can be seen that ux will flow from poles 11 and`12 on stator 11)' into pole 31 on rotor 30, through rotor 30, and out of pole 3S into poles 25 and 26 on stator 10 to complete the magnetic circuit. Also, flux will ilow out of poles 19 and 2t) on stator 1@ into pole 35 on rotor 30, through rotor 30 to pole 34, and -thence into poles 17 and 18 on stator 10 to complete the magnetic circuit. While the rotor is in this position and the torque generator control iield windings 77 and 82 are deenergized it can be seen that no torque is produced on rotor 311'. Therefore, the rotor 30 is in a null position for the torque generator. The rotor would also be at a null if terminal 65 on terminal board 11) were positive. This is true because all of the vpoles of the torque generator would be exactly opposite, magnetically, to the explanation above. That is, the north poles would then be south poles and the south poles would then be north poles.

It should be noted that any pole on the rotor 3@ can be aligned between any two poles on the stator and the rotor will be in a null position. However, this does not necessarily mean that the device attached to the rotor is in its proper position. Thus, some means of torquing or turning the rotor so that the device attached to it is in its proper position must be added. This is done by applying a control voltage to terminals 151 and 153 on terminal board 135.

Assume that the torque generator pattern field windings are energized as previously described. That is, terminal 73 on terminal board 110 has a positive voltage applied thereto. Also, assume terminals 153 and 151 have an alternating voltage applied thereto and, momentarily, terminal 75 on terminal board 111D is positive. The current iiowing through the torque generator control eld winding, coils 77 and 82, will cause poles 17, 2t), 25 and 12 to look like south poles, and poles 18, 19, 26 and 11 to look like north poes. As previously explained, the current ilowing through the torque generator pattern iield winding, coils 67 and 71, will make poles 17, 18, 25 and 26 look like south poles and poles 19, 2), 11 and 12 look like north poles. Thus, thefiux caused by the torque generator pattern field windings 67 and 71 and the flux caused by the torque generator control iield windings 77 and 82 will cancel each other out in poles 18, 2t), 25 and 12. The flux in poles 17 and 25 will add to make these appear as south poles and the flux in poles 19 and 11 will add to make them appear as north poles. Therefore, because of the magnetic flux on one side ofthe device ilowing from pole 19, through pole 35 on rotor 3th, out

of pole 34 on rotor 30, and into pole 17 on the stator Y 10; and the magnetic tlux on the other side of the device flowing out of pole 11 on stator 10 into pole 31 on rotor 31B, and out of pole 38 on rotor 30 into pole 25 .on stator 1o, Ya clockwise torque will be applied to rotor 3th This torque will tend to radially align pole 17 on stator 10 and pole 34 on rotor 30, pole 19 on stator 10 and pole 35 on rotor 3), pole 25 on stator 10 and pole 38 on rotor 30 and pole 11 on stator 10 and pole 31 on rotor 30. Thus, it can be seen that a torque can be applied to rotor 30 by applying a control voltage to erminals 151 and 153 on terminal board 135 or, in other words, the torque generator control eld winding.

In some of the prior art devices both of the windings of the torque generator and both'of the windings of the signal generator were disposed about all of the poles of the stator. That is, each winding was wound entirely around the stator. This method of winding caused a large quantity of interaction between the torque generator ux and the signal generator tlux, and any attempt to make a tight loop by applying the signal generator output to ahigh gain ampliiier and the output of the high gain amplifier to the torque generator control pattern field rei? sulted in oscillations. These oscillations could take the form of the rotor itself oscillating or, in some cases, simply electrical oscillations in the circuitry. However, by restricting the torquer to two diametrically oppgosite quadrants of the stator and the signal generator to two diametrically opposite quadrants of the stator some of this interaction is eliminated.

In the present invention the balance winding, coils 87 and 89, has been added to eliminate the rest of the interaction between the signal generator and the torque generator. This is accomplished by winding the balance winding about the torque generator poles as already described. Thus, a voltage is induced in the balance winding which tends to vary in the same manner as the error signal which is induced in the signal generator secondary winding by the torque generator winding. The voltage induced in the balance winding varies in the same manner as the error signal but they are not necessarily of the same magnitude. Thus, the circuitry shown in FIGURE 3 is utilized. That is, one side of the signal generator secondary winding coil 43 connects by means of lead 83 to what is effectively the center tap of the balance winding. in this manner a reference is established, and the variable arm of'variable resistor 126, which is effectively in parallel with the windings of the balance winding will simply have the signal generator secondary winding voltage on it when it is in the center of its movable range. However, by moving the arm of resistor 12d towards resistor 128 the voltage induced in the balance winding will be added to the voltage induced in the signal generator secondary winding, and by moving the arm toward resistor 131 the voltage induced in the balance winding will be subtracted from the signal generator secondary winding voltage. Thus, any fluctuations induced in the signal generator secondary winding due to the torque generator can be completely eliminated by setting the arm of potentiometer 126 to a given position. This device has eliminated the coupling between the signal generator and the torque generator so effectively that the gain of an amplifier connecting the signal generator secondary winding output to the torque generator control field winding input may be improved by approximately a factor of twenty.

The function of the compensation winding is to compensate for non-acceleration produced torques acting on the rotor. These torques could be produced by the device which is attached to the rotor, which in this example would be the gimbal of a gyro, or they could be due to the rotor and stator of the device described not y being perfectly symmetrical, or they might be due to some mechanical or electrical discrepancies, such as winding dissimilarities. By referring to FIGURE 3 it can be seen that the coils 94 and 93 of the compensation winding are effectively in series with the torque generator pattern field winding.

be noted, however, that the compensation winding ismuch smaller than the torque generator control field winding. The amount of torque which the compensation winding produces on rotor 30 is proportional to the amount of current iiowing through the coils 94- and 98 of the compensation winding, and the direction of the K torque on rotor 3d will depend upon the sense in which coils 94 and 98 are connected in the circuit. Thus, any non-acceleration produced torques acting on the rotor are effectively cancelled.

It can also be seen that resistor 142 is effectively in parallel with the compensation winding.

. Because of the nonsymmetry in the mechanical and electrical structure of devices such as the one described a `common source of trouble is the non-coincidence of the signal generator and the torque generator nulls. This problem can be seen more clearly by assuming the signal `generator is at a null and the torque generator is slightly off null. At this time a voltage will be induced in the torque generator control field winding by the torque generator pattern field winding, and this voltage will be fed back to the source of control signal voltage. Conversely, when the torque generator is at la null and the signal `generator is slightly off null the signal generator'winding will be producing a signal. Referring to FIGURE 3, the primary winding 112 of variable transformer ill is connected in series with coils it? and 41 of the signal generator primary winding. The secondary winding T22 iof variable transform-er iii is connected in series with the coils 42 and i3 of the signal generator secondary winding and the balance circuit, coils 87 and 89, previously described. The variable transformer lill is adjusted so that when the torque generator is at a null the secondary 122 .of variable transformer `ill has induced in it the same amount of lvoltage as is induced in coils i2 `and 43 of the signal generator secondary winding by the primary winding, coils 4l and dil. Thus, by connecting the secondary 122 of variable transformer ill in series with coils d2 and 423 of the signal generator secondary but in the opposite sense the two equal voltages cancel and the signal generator is at a null, or the net output voltage is zero, in the same mechanical position as the torque generator.

Since the non-'coincidence of the nulls of the signal generator and the torque generator is a constant, once the adjustment of variable transformer "111 is accomplished it will compensate :for the non-coincidence of the nulls throughout the entire range of rotor Etls movements. Also, any Variation-s in the alternating voltage applied to terminals 115 and 12T of terminal board 126, or, effectively, the signal generator primary winding will be compensated for. Thus, it can be seen that a novel and effective method for eliminating interaction between the signal generator and torque generator windings, non-coincidence of signal generator and torque generator nulls, and torques on the rotor due to non-symmetrical mechanical and electrical construction has been lprovided for. The above described invention has greatly reduced problems and has greatly increased the accuracy and sensitivity in the control apparatus described.

While i have shown and described a specific embodiment of this invention, further modifications and improvements 'will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular `form shown and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.

I claim:

1. in apparatus of the class described: a cylindrical stator composed of magnetic material, said stator having a first and second set of poles radiating inward toward a central axis and forming a central aperture therebetween, said first set of poles being contained within a first and second quadrant of said cylindrical stator, said first and second quadrants being diametrically opposite, and said second set of poles being contained within a third and fourth quadrant of said cylindrical stator, said third and `fourth quadrants being diametrically Opposite; a cylindrical rotor composed of magnetic material, said rotor having a plurality of poles radiating outward from a central axis, the #outer diameter of Isaid cylindrical rotor and said poles aiiixed thereto being smaller than the inner diameter of said central aperture of said cylindrical stator; means rotatably mounting said rotor within said aperture of said stator so as to lform a symmetrical air gap therebetween; a variable transformer having a primary and a secondary winding; primary winding means lbeing disposed about said iirst set of poles; means connecting said i i primary of said variable transformer in4 series with said primary winding means `and adapted to have an alternating voltage Vapplied thereto; secondary winding means adapted to have induced therein an alternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position of said stator and said rotor, said `secondary winding means being disposed about said first set of poles; pattern field winding means bein-g disposed about said second set of poles; control field winding means adapted to be connected to an alternating voltage, said control field winding means being disposed about said second set of poles, said pattern field winding mean-s and said control field winding means producing -a 4torque on said rotor when connected -to suitable alternating voltages; balance winding means disposed about said second set orf poles; means connecting said balance winding means, said secondary ywinding of said variable transformer, `and said secondary winding means in series and adapted to have a load applied thereto; compensation winding means disposed about said -second set of poles; and means connecting said compensation winding means in series with said pattern field and adapted to have an alternating voltage applied thereto.

2. In apparatus of the class described: a cylindrical stator composed of magnetic material, said stator having a first and second set of poles radiating inward toward a central axis and forming a central aperture therebetween, said first set of poles being contained within a first and second quadrant of said cylindrical stator, said first and second quadrants being diametrically opposite, and said second set of poles being contained within a third and fourth quadrant of said cylindrical stator, said third and fourth quadrants being diametrically opposite; a cylindrical rotor composed of magnetic material, said rotor having aplurality of poles radiating outward from a central axis, the outer diameter of said cylindrical rotor and said poles affixed thereto being smaller than the inner diameter of said central aperture of said cylindrical stator; means rotatably mounting said rotor within said aperture of said stator so as to form a symmetrical air gap therebetween; primary winding means being disposed about said first set of poles and adapted to have an alternating Voltage applied thereto; secondary winding means adapted to have induced therein an alternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position Yof lsaid stator and said rotor, said secondary winding means being disposed about said first set of poles; pattern field winding means being disposed about said second set of polesg'control field winding means adapted to be connected to an alternating voltage, said control field winding means being disposed about said second set of poles, said pattern field winding means and said control field winding means producing a torque on said rotor when connected to suitable alternating voltages; balance winding means disposed about said second set of poles; means connecting said balance Winding means and said secondary winding means in series and adapted to have a load applied thereto; compensation winding means disposed about said second set of poles; and means connecting said compensation winding means in series with said patern field and adapted to have an alternating voltage applied thereto.

3. In apparatus of the class described: a cylindrical stator composed of magnetic material, Said stator having a first and second set of poles radiating inward toward a central axis and forming a central aperture therebetween; a cylindrical rotor composed of magnetic material, said rotor having a plurality of poles radiating outward from a central axis, the outer diameter of said cylindrical rotor and said poles aiiixed thereto being smaller than the inner diameter of said central aperture of said cylindrical stator; means rotatably mounting said rotor within said aperture of said stator so as to form a sym- Y metrical air gap"ther`ebetween;l a variable transformer Ahaving a primary and a secondary winding; primary winding lmeans being disposedabout said first set of poles; means connecting said primary of said variable transformer in series with said primary winding means and adapted to have an alternating voltage appliedl thereto; secondary winding means adapted to have induced therein an alternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position of said stator and said rotor, said secondary winding means being disposed about said first set of poles; pattern eld winding means being disposed about said second set of poles; control field winding means adapted to be connected to an alternatingvoltage, said control field winding means being disposedV about said second set of poles, said pattern field winding means and said control field winding means producing a torque on said rotor when connected to rsuitable alternating voltages; balance winding means disposed about said second vset of poles; means connecting -said balance winding means, said secondary winding of said variable transformer, and said secondary winding means inseries and adapted to have a load applied thereto; compensation winding means disposed about said second set of poles;

`and means connecting said compensation winding means in series with said pattern field and adapted to have an alternating voltage applied thereto.

4. In apparatus of the class described: a cylindrical stator composed of magnetic material, said stator having a first and second set of poles radiating inward toward a central axis and forming a central aperture therebetween, said first set of poles being contained within a first and second quadrant of said cylindrical stator, said first and second Yquadrants being diametrically opposite, and said l second set of poles being contained within a third and gap therebetween; a variable transformer having a primary and asecondary winding; primary' winding means being disposedaboutsaidrst set of poles; means connecting said primary of said variable transformer in series with said primary winding means and adapted to have an alternatngvoltage applied thereto; secondary winding means adapted to have induced therein an alternating voltage as a Afunction of the magnitude of the voltage applied'to said primary winding means and of the relative position of said stator andsaid rotor, said secondary winding means being disposed about said first set of poles; pattern field winding means being disposed about said second set of poles and adapted to have an alternating voltage applied thereto; controlY field winding means adapted to be connected to an alternating voltage, said control field Winding means being disposed about said second set of poles, said patternfield winding means and said control field winding means producing a torque on said rotor when connected to Isuitable alternating voltages; balance winding means disposed about said second set of poles; and means connecting said balance winding means, said -secondary winding of said variable transformer, and said secondary winding means in series and adapted to have acload applied thereto.

5. In apparatus of the class described: a cylindrical stator composed of magnetic material, said stator having a first and secondset of poles radiating inward toward a central axis and forming al central aperture therebetween, said first set of poles being amxed to a first and a second arc of said cylindrical stator, said first and second arcs being diametrically opposite, and said second set of poles being affixed to a third and a fourth arc of said lit cylindrical stator, said third and fourth arcs being diametrically opposite; a cylindrical rotor composed of magnetic material, said rotor having a plurality of poles radiating outward from a central axis, the outer diameter of said cylindrical rotor and saidpoles atlixed thereto being smaller than the inner diameter of said central aperture of said cylindrical stator; means rotatably mounting said rotor within said aperture of said stator so as to form a symmetrical air gap therebetween; a Variable transformer having a primary and a secondary winding;

'primary winding means being disposed about said rst set of poles; means connecting said primary of said variable transformer in series with said primary winding means and adapted to have an alternating voltage applied thereto; secondary winding means adapted to have induced therein a nalternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position of said stator and said rotor, said secondary winding means being disposed about said iirst set of poles; pattern field winding means being disposed about said second set of poles; control field winding means adapted to be connected to an alternating voltage, said control iield winding means being disposed about said second set of poles, said pattern field winding means and said control eld winding means producing a torque on said rotor when connected to suitable alternating voltages; balance winding means disposed about said second set of poles; means connecting said balance winding means, said secondary winding of said variable transformer, and said secondary winding means in series and adapted to have a load applied thereto; compensation winding means disposed about said second set of poles; and means connecting said compensation winding means in series with said pattern iield and adapted to have an alternating voltage applied thereto.

6. In apparatus of the class described: a stator, a

rotor; means mounting said rotor in juxtaposition with said stator and allowing relative movement therebetween; signal generating means mounted on said stator, said signal generating means producing a signal dependent upon the relative position of said stator and said rotor; torque generating means mounted on said stator and adapted to have a signal applied thereto, said torque generating means producing a torque on said rotor when a signal is applied thereto; null compensating means; means connecting said null compensating means to said signal generating means, said null compensating means causing said signal generating means to produce a zero signal when said torque generating means is producing zero torque; and compensating means mounted on said stator, said compensating means compensating for substantially any interaction between said signal generating means and said torque generating means.

7. In apparatus of the class described: a stator, a movable member; means mounting said movable member in juxtaposition with said stator and allowing relative movement therebetween; signal generating means mounted on said stator, said signal generating means producing a sig nal dependent upon the relative position of said stator and said movable member; force generating means mounted on said stator and adapted to have a signal applied thereto, said force generating means producing a force on said movable member when a signal is applied thereto; null compensating means; means connecting said null compensating means to said signal generating means, said null compensating means causing said signal generating means to produce a zero signal when said force generating means is producing zero force; and compensating means mounted on said stator, said compensating means compensating for substantially any interaction between said signal generating means and said force generating means.

8. In apparatus of the class described: a cylindrical Y ystator composed of magnetic material, said stator having ars't and second set of poles radiating inward toward a 'A central axis and forming a central aperture therebetween,

id said rst set of poles being contained within a lirst and second quadrant of said cylindrical stator, said first and second quadrants being diametricauy opposite, and said second set of poles being contained within a third and fourth quadrant of said cylindrical stator, said third and fourth quadrants being diametrically opposite; a cylindrical rotor composed of magnetic material, said rotor having a plurality of poles radiating outward from a central axis, the outer diameter of said cylindrical rotor and said poles aixed thereto being smaller than the inner diameter of said central aperture of said cylindrical stator; means rotatably mounting said rotor within said aperture of said stator so as to form a symmetrical air gap therebetween; a variable transformer having a primary and a secondary winding means being disposed about said first set of poles; means connecting said primary of said variable transformer in series with said primary winding means and adapted to have an alternatin7 voltage applied thereto; secondary winding means adapted to have induced therein an alternating voltage as a function of the magn-itude of the voltage applied to said primary winding means and of the relative position of said stator and said rotor, said secondary winding means being disposed about said first set of poles; pattern lield winding means being disposed about said second set of poles; control lield winding means adapted to be connected to an alternating voltage, said control field winding means being disposed about said second set of poles, said pattern iield winding means and said control field winding means producing a torque on said rotor when connected to suitable alternating voltages; compensation winding means disposed about said second set of poles; and means connecting said compensation winding means in series with said pattern field and adapted to have an alternating voltage applied thereto.

9. In apparatus of the class described: a stator, a rotor; means mounting said rotor in juxtaposition with said stator and allowing relative rotation therebetween; signal generating means mounted on said stator, said signal generating means producing a signal dependent upon the relative position of said stator and said rotor; torque generating means mounted on said stator and adapted to have a signal applied thereto, said torque generating means producing a torque on said rotor when a signal is applied thereto; null compensating means, comprising a means, said null compensating means causing said signal generating means to produce a zero signal when said torque generating means is producing Zero torque; and compensating means mounted on said stator, said compensating means compensating for substantially any interaction between said signal generating means `and said torque generating means.

10. In apparatus of the class described: a stator, a movable member; means mounting said movable member in juxtaposition with said stator and allowing relative movement therebetween; signal generating means mounted on said stator, said signal generating means producing a signal dependent upon the relative position of said stator and said movable member; force generating means mounted on said stator and adapted to have a signal applied thereto, said force generating means producing a force on said movable member when a signal is applied thereto; null compensting means, comprising a variable transformer and winding means, said winding means being disposed about said stator; means connecting said null compensating means to said signal generating means, said null cornatrasos and second set of poles; a movable member composed of magnetic material, said movable memberfhaving a plurality of poles affixed thereto; means movably mounting said movable member in juxtaposition with said stator so as to form a symmetrical air gap therebetween; a variable transformer having a primary and a secondary winding; primary winding means being disposed about said first set of poles; means connecting said primary of said variable transformer in series with said primary winding means and adapted to have an alternating voltage applied thereto; secondary winding means adapted to have induced therein an alternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position of said stator and said movable member, said secondary winding being disposed about first set of poles; pattern field winding means being disposed about said second set of poles; control field Winding means adapted to be connected to an alternating voltage, said control field-winding means being disposed about said second set of poles, said pattern field winding means and said control field winding means producing a force on said movable member when connected to suitable alternating voltages; balance winding means disposed about said second set of poles; means connecting said balance winding means, said secondary winding of said variable transformer, and said secondary winding means in series and adapted to have a load applied thereto; compensation winding means disposed about said second set of poles; and means connecting said compensation winding means in series with said pattern field and adapted to have an alternating voltage applied thereto.

12. In apparatus of the class described: a stator composed of magnetic material, said stator having a firstand second set of poles; a movable member composed of magnetic material, said movable member having a plurality of poles affixed thereto; means movably mounting vsaid movable member in juxtaposition with said stator so as to form a symmetrical air gap therebetween; a variable transformer having a primary and secondary winding; primary winding means being disposed about said first-set of poles; means connecting saidprimary of said variable transformer in series vwith said primary winding means and adapted to have an alternating voltage applied thereto; secondary winding means adapted to have induced therein an alternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position of said stator and said movable member, said secondary winding means being disposed about said first set of poles;

pattern field winding means being disposed about said second set of poles; control field winding means adapted to be connected to an alternating voltage, said control fiield winding means beingdisposed about said second set of poles, said pattern field Winding means and said control field winding means producing a force on said movable member when connected to suitable alternating votages; compensation winding means disposed about said second set of poles; and means connecting said compensation windingmeans in series with sa1d pattern field and adapted to have an alternating voltage Yapplied thereto.

13. In apparatus of the class described: a stator composed of magnetic material, said stator having a first and second set of poles; ak movable member composed of magnetic material, said movable member having a lili' fand said movable member, said secondary windingv means being disposed about said first set of poles; pattern field winding means being disposed about said second set of poles; control field winding means adapted to be ,connected to an alternating voltage,said control field winding means being disposed about said second set of poles, said pattern field winding means and -said control field winding means producing a force on said movable member when connected to suitable alternating voltages; balance winding means disposed about said second set of poles; means connecting said balance Winding means and said secondary winding means 4in series and adapted to have a load applied thereto; compensation winding means disposed about said second set of poles; and means connecting said compensation winding means in series with saidrpattern yfield and adapted to have an alternatingv voltage applied thereto.

14. In apparatus o-f the class described: a stator composed of magnetic material, said stator having a first and second set of poles;va movable member composedeof magnetic material, said movable member having a plurality of poles atixed thereto; means movably mounting said movable member in juxtaposition `with said stator so as to form a symmetrical air gap4 therebetween; a variable Vtransformer having a primary and a secondary winding; primary winding means being disposed about .said

first set of poles; means connecting said primary of said variable transformer in series with said primary 4winding means and adapted tot have an alternating voltage applied thereto; secondary Winding means adapted to have induced therein an alternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position of said stator and said movable member, said secondary winding means being disposed about said first set of poles; patterncfield winding means being disposed about said second set of poles; control field winding means adapted yto be connected to an alternating voltage, said control, field winding means bef winding of said-variable transformer, and said secondary winding means in series and adapted to have a loadapplied thereto.

l5. In apparatus of the class described: a stator composed of magnetic material, said stator having a plurality of poles afiixed thereto; a movable member composed of magnetic material, said movable member having a plurality of poles affixed thereto; means movably mounting said movable member in juxtapositionwith said stator so as to form a symmetrical air gap therebetween; a variable transformer having a primary anda secondary winding; primary Winding means being disposed about said poles affixed to said stator; means connecting said primary of said variable transformer in series with said primary winding means and adapted to have an alternating voltage applied theneto; secondary winding means adapted to have induoed therein an alternating voltage as a function of the magnitude of the voltage applied to said primary winding means and of the relative position of said stator and said movable member, said secondary winding means being disposed about said poles affixed to said stator; pattern field winding means being disposed about said poles affixed to said stator; control field winding means adapted to be connected toy an alternating voltage, said control field winding means being disposed about said poles affixed to said stator, said pattern field winding means and said control field winding means producing a force on said movable member when connected to suitable alternating voltages; balanoe winding means disposed aboutsaid poles affixed to saidstator; means connecting 17 18 said balance Winding means, said secondary winding of References Cited bythe Examiner said variable transformer, and said secondary Winding UNITED STATES PATENTS means in series and adapted to have a gload applied there- T to; compensation Winding means disposed about said irrlrolg '14T/ 425% POIeS 0f Said stator? and means Connecting Said com' 5 2'908168 10/59 Maynard 74-56 pensation Winding means in series with said pattern eld and adapted to have an alternating voltage applied MILTON O. HIRSHFIELD, Primary Examiner. thereto. DAVID X. SLINEY, Examiner. 

7. IN APPARATUS OF THE CLASS DESCRIBED: A STATOR, A MOVABLE MEMBER; MEANS MOUNTING SAID MOVABLE MEMBER IN JUXTAPOSITION WITH SAID STATOR AND ALLOWING RELATIVE MOVEMENT THEREBETWEEN; SIGNAL GENERATING MEANS MOUNTED ON SAID STATOR, SAID SIGNAL GENERATING MEANS PRODUCING A SIGNAL DEPENDENT UPON THE RELATIVE POSITION OF SAID STATOR AND SAID MOVABLE MEMBER; FORCE GENERATING MEANS MOUNTED ON SAID STATOR AND ADAPTED TO HAVE A SIGNAL APPLIED THERETO, SAID FORCE GENERATING MEANS PRODUCING A FORCE ON SAID MOVABLE MEMBER WHEN A SIGNAL IS APPLIED THERETO; NULL COMPENSATING MEANS; MEANS CONNECTING SAID NULL COMPENSATING MEANS TO SAID SIGNAL GENERATING MEANS, SAID NULLY COMPENSATING MEANS CAUSING SAID SIGNAL GENERATING MEANS TO PRODUCE A ZERO SIGNAL WHEN SAID FORCE GENERATING MEANS IS PRODUCING ZERO FORCE; AND COMPENSATING MEANS MOUNTED ON SAID STATOR, SAID COMPENSATING MEANS MOUNTFOR SUBSTANTIALLY ANY INTERACTION BETWEEN SAID SIGNAL GENERATING MEANS AND SAID FORCE GENERATING MEANS. 